Access points as radio relay stations for a wireless LAN are used as the device for connecting multiple computers at separate locations to, e.g., the Internet or, in general, to a Wide Area Network (WAN). Access points may be adapted to give authorization for access to the Internet via the wireless LAN only to a limited number of people (for example clients). In such cases, it is required to prevent illegal access of any unauthorized person to the network. Moreover, for a sufficient protection of the privacy of each person, it is essential to effectively prevent the contents of communication between the computers from being leaked to any third person by interception of the radio waves in the radio communication area associated to the access point.
Diverse security techniques for preventing illegal access to the network and leakage of communication to any third person have been proposed with regard to the wireless LAN: one proposed technique utilizes a MAC (Media Access Control) address, which is an intrinsic identification number allocated to a device for connecting the wireless LAN (for example, a wireless LAN adapter) attached to the terminal, and registers the allocated MAC address in the access point. The access point authenticates the MAC address in response to an access from the terminal, and rejects the request of access to the network from the terminal when the input MAC address is not identical with the registered MAC address.
Another proposed technique sets a WEP (Wired Equivalent Privacy) key as a common encryption key in both the terminal and the access point and encrypts the details of the data, which are transmitted between the terminal and the access point, with the WEP key. Even in the case of accidental leakage of data, the encryption makes it difficult to analyse and grasp the data.
The prior art security technique, however, requires manual registration of the MAC address in the access point and manual setting of the WEP key in the terminal. This is rather troublesome and inconvenient in the case of new enrollment of a terminal for the wireless LAN.
A WEP key of an arbitrary letter string set in the terminal should also be set in the access point. It would be preferable to utilize the wireless LAN for the setting. In this scenario, the WEP key data carried on the radio wave is transmitted from the terminal to the access point by wireless. The access point receives the transmitted WEP key and sets the WEP key mapped to the terminal. The user of the terminal is then allowed to enjoy various services (for example, Internet access service) via the wireless LAN immediately after transmission of the WEP key. In the case of wireless transmission of the WEP key, however, there is a possibility of leakage of the WEP key to a third person through interception of the radio wave transmitted between the terminal and the access point. The third person who illegally obtains the leaked WEP key can analyse and grasp all the data transmitted between the access point and the terminal with the WEP key. This disables the security system based on encryption.
US 2004/0076300 discloses a method and an arrangement which allows for a new enrollment of a terminal for a WLAN, while preventing leakage of data representing an encryption key, wherein in response to the pressure of a registration button, an access point restrict the coverage of radio wave transmitted from the access point from a general radio communication area to a narrower security communication area. The access point subsequently delivers a Wired Equivalent Privacy (WEP) key to a terminal, confirms the successful delivery, and registers a Media Access Control (MAC) address of the terminal, which sets the delivered WEP key in it.
Additionally, US 2004/0023642 discloses a wireless access point for connecting a wireless LAN and a wired LAN together comprising a central control unit able to read a bridge control program, an IEEE 802.1x control program and an authentication control program into a memory, to execute them. Based upon the IEEE 802.1x control program and the authentication control program, the central control unit authenticates a wireless terminal on a wireless LAN in response to a request for access to a network on a wired LAN from the wireless terminal on the wireless LAN, and notifies a common key of WEP to the wireless terminal on the wireless LAN when the authentication is obtained. A certificate issue program is further stored in the wireless access point. In fact, when an EAP-TLS system which is one of the authentication system, is used, a certificate issue server function is necessary for issuing a valid certificate for authenticating the client. The central control unit reads the certificate issue program to execute it. Based on the certificate issue program, the central control unit forms a certificate for the client in the wireless access point. The certificate for the client that is formed is sent to, for example, an IC card reading/writing device on the reliable network on the wired LAN through a wireless LAN interface unit. The IC card reading/writing device prepares an IC card recording the certificate for the client for the predetermined wireless terminal. In the network system equipped with this wireless access point a wireless terminal on the wireless LAN can be authenticated at the wireless access point eliminating the need of providing the authentication server and the certificate issue server on the wired LAN. In this way a packet for authentication exchanged among the wireless access point, the authentication server and the certificate issue server is prevented from flowing on the wireless LAN and therefore from being eavesdropped.
Furthermore, the Bluetooth® Security White Paper (which can be downloaded, as of the filing date of the present specification, from the Internet at the Bluetooth® website from a file entitled “24Security Paper.PDF) discloses a procedure to set up a trusted connection between two terminals controlled by the same user and initially unknown, wherein the procedure is based on the performance of a physical action on the two terminals by the user, and on the user's knowledge of a secret key stored in one of the two terminals. Authentication is performed by asking the user to type the secret key in the other terminal.
The Applicant has observed that, this procedure firstly implements an authentication protocol which is based on a shared secret keys and therefore can suffer from the problem of weakness against so-called “vocabulary” attacks, and secondly requires that the user remember and types a secret key for each of the terminals to be authenticated.